1. Field of the Inventions
The field of the invention relates generally to osmolarity measurements and more particularly to the use of a contact lens as an ex-vivo receiving substrate to collect tears for subsequent tear film osmolarity measurements.
2. Background Information
Tears fulfill an essential role in maintaining ocular surface integrity, protecting against microbial challenge, and preserving visual acuity. These functions in turn, are critically dependent upon the composition and stability of the tear film structure, which includes an underlying mucin foundation, a middle aqueous component, and an overlying lipid layer. Disruption, deficiency, or absence of the tear film can severely impact the eye.
An increased salt concentration (osmolarity) of the human tear film has been identified as the underlying causative mechanism for all types of dry eye. Chronically heightened osmolarity is tied to post-LASIK complications, keratoconjunctivitis sicca, and contact-lens induced dry eye. While its usefulness as a marker of tear film health is evident, the ability to rapidly measure tear osmolarity has eluded science for decades. If it were possible to measure and, more importantly, monitor the relative tear film osmolarity over time, the quality of health care that could be provided to dry eye patients would increase dramatically. Personalized data about the state of one's disease would allow physicians to develop new therapies, alter prescriptions, and modulate the type of products used in a timely fashion.
For example, the day-to-day response of the tear film is of particular interest when challenged by the deleterious effects of contact lens wear. Irritation caused by contact lenses may lead to an inflammatory condition that exacerbates dry eye symptoms and causes lens wearers considerable discomfort. Often, when getting fitted for a new prescription, a patient must try several different types of lenses before finding a brand that is optimized for their individual ocular surface. The fitting process is largely trial and error because the clinician lacks the ability to track the patient's response over time. Further, because deleterious inflammatory effects may take a few hours to days to occur, it is not feasible to gather this data while the patient is sitting in a clinician's office.
The same constraints hold for monitoring the efficacy of dry eye therapeutics, whether pharmaceutical, tear replacement, or mechanical, i.e. goggles, punctal plugs, etc. Physicians have no means to collect, or correlate patient data, i.e. race, age, gender, medications taken, etc. with signs and symptoms over time. Likewise, scientists would benefit greatly from this data when developing new techniques to treat the disease.
Prevalent technologies require collection of tears by gently touching a glass capillary to the lower lid. However, such technologies are not amenable to “at home” testing. Furthermore, the clinical equipment necessary to analyze the tear film is far too expensive for personal monitoring of tear film health.